1. Field of the Invention
This invention relates to a cylinder lock of the type comprising a housing, a cylinder core mounted for rotation in said housing, a slot extending into the cylinder core parallel to the rotational axis thereof, for receiving a key, at least one row of locking pins guided in bores in said cylinder core and being movable against spring means by a key which engages ends of the pins when the key is inserted into the slot, and at least one side bar accommodated in a recess extending axially in a peripheral part of the cylinder core, the or each side bar being spring biassed outwardly of the cylinder into engagement with a recess in the housing which recess is shaped to retract the side bar into the cylinder core upon turning the cylinder core. In such a lock, turning of the cylinder core is dependent upon the correct key being inserted to place the locking pins in respective positions in their bores to permit retraction of the side bar.
2. Description of Prior Art
U.S. Pat. No. 2,070,333 (Liss) discloses a lock of the kind set forth above, having two side bars which co-operate with a single row of locking pins which have pointed ends and are controlled by a coded surface of sawtoothed appearance provided along the edge of the blade of a key. The locking pins are provided with waisted portions at different locations along the various pins, and the side bars can retract to permit turning of the cylinder of the lock when the pins have been set that their waisted portions line up with the side bars.
The side bars are relatively thin, and have straight edges which engage the locking pins (which are of circular section). Thus wear is likely to occur at the regions of contact between the pins and side bars, and in addition wear is likely to occur between the pointed ends of the pins and the key. In addition to these disadvantages, the pins must be made to great accuracy.
A further form of cylinder lock is disclosed in U.S. Pat. No. 3,080,744 (Spain), in which lock a side bar co-operates with flat tumblers of identical form, the side bar having differently located recesses along its length. However, lever tumblers as disclosed are highly subject to wear by engagement with the key, and the number of possible combinations which can be achieved in a lock of a given size is comparatively small because available space is not fully utilised.
Yet another lock construction is described in U.S. Pat. No. 3,035,433 (Testa). This lock has a side bar which co-operates with flat lever tumblers, and requires the provision of many different shapes of lever tumbler. Further, the conditions under which the side bar and tumbler levers engage can cause the side bar readily to become jammed.
Yet further forms of lock are described in Swedish patent specification No. 385,228 (Medeco) and U.S. Pat. No. 3,499,302 (Spain).